QMediaPlayer播放MP3无声音解决办法

QT中利用QMediaPlayer播放MP3无声音，程序运行时提示：
“QtMultimedia : defaultServiceProvider::requestService(): no service found for – “org.qt-project.qt.mediaplayer”
调试跟踪错误信息，提示：
“A valid playback service was not found, playback cannot proceed.”

原因是系统中在Linux中缺少libqt5multimedia5-plugins 库文件，安装后解决：

sudo apt install  libqt5multimedia5-plugins

完成例子源代码：

mainwindows.h

<code>#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QtMultimedia/QMediaPlayer>
#include <QtMultimedia/QMediaPlaylist>
#include <QDir>
#include <QRandomGenerator>

QT_BEGIN_NAMESPACE
namespace Ui {
class MainWindow;
}
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
    QMediaPlayer *player;
    QMediaPlaylist *playlist;
    QList<QFileInfo> *fileInfo;
    QDir *dir;
    int mp3count;

private slots:
    void on_pushButton_clicked();
    void on_pushButton_2_clicked();

private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
</code>

mainwindows.cpp

#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    // 播放器
    player = new QMediaPlayer;
    // 播放错误信息
    connect(player, QOverload<QMediaPlayer::Error>::of(&QMediaPlayer::error),
    [=](QMediaPlayer::Error error) {
        qDebug()<<error;
    });

    // 生成播放列表
    playlist = new QMediaPlaylist(player);
    dir=new QDir("/home/pi/Music");  // mp3存放目录
    QStringList filter;
    filter<<QString("*.mp3");
    fileInfo=new QList<QFileInfo>(dir->entryInfoList(filter));
    for(int i = 0; i<fileInfo->count(); i++)
    {
        qDebug()<<fileInfo->at(i).filePath();
        playlist->addMedia(QUrl::fromLocalFile(fileInfo->at(i).filePath()));
        ui->textEdit->append(fileInfo->at(i).filePath());
    }

    player->setPlaylist(playlist);
    mp3count = fileInfo->count();
    qDebug()<< "Mp3 count : "<< mp3count << endl;
}

MainWindow::~MainWindow()
{
    delete ui;
}


void MainWindow::on_pushButton_clicked()
{
    // 随机播放mp3
    player->stop();
    player->setPlaylist(playlist);
    int i = QRandomGenerator::global()->bounded(fileInfo->count());
    playlist->setCurrentIndex(i);

    qDebug()<< "Mp3 index : "<< i << ", name:"<< player->currentMedia().canonicalUrl();;
    player->setVolume(50);
    player->play();
}

void MainWindow::on_pushButton_2_clicked()
{
    // 播放指定mp3
    player->setMedia(QUrl::fromLocalFile("/home/pi/Music/红日.mp3"));
    qDebug()<< player->currentMedia().canonicalUrl();
    player->setVolume(50);
    player->play();

}